Mac users interested in Spoutcraft 1.8 generally download:
Spoutcraft connects the server and client which makes most of the Spout features possible. Some things such as inventory monitoring and the server speed improvements only require the Spout server plugin. Any player can connect to a Spout enabled server; they will just miss out on the features it has to offer. Spoutcraft is optional, but using it unlocks the real features behind the Spout plugin.